New Aid for Storm Forecasters

But what may be the lasting impression of Wilma is its rapid strengthening -- and what it reveals of forecasters' gaps in knowledge. Before striking Mexico, Wilma exploded over a 24-hour period from a tropical storm to a raging Category 5 hurricane.

It was superlative in many respects. The speed of its development is believed to have been unprecedented. It had at one point the smallest eye known to the National Hurricane Center staff -- two nautical miles in diameter -- and the central pressure at the time of peak intensity was a record low for an Atlantic hurricane.

"It is fortunate that this ultra-rapid strengthening took place over open waters, apparently void of watercraft, and not just prior to landfall," the tropical cyclone report on Wilma says in the understatement typical of such reports.

Forecasters did a relatively decent job at predicting its track, according to the report. But it noted that the errors in predicting intensity were "quite a bit larger than the average."

Predicting storm intensity is considered a critical challenge among forecasters because so many people depend upon forecasts of intensity to determine whether to flee an oncoming storm.

Emergency managers determine evacuation orders depending on the predicted intensity. Residents make their own calculations regarding whether to obey.

Coastal residents of the southeastern states have long been familiar with hurricane forecasts, and many simply ignore evacuation calls if the approaching tropical cyclone is a Category 1 or even a Category 2.

The uncertainty in the forecast intensity and track of storms forces emergency managers to make broader preparations than might be necessary, and when they prove unnecessary the inconvenience dulls the public's willingness to take precautions the next time.

"We have to base our evacuations on a worst-case scenario," said Jonathan Lord, an emergency manager in Miami-Dade County, noting that evacuation orders there assume that the storm will be one category stronger than forecast. "Look what happened to Wilma overnight."